Kuppers, Bernd-Olaf. “Understanding Complexity.”

According to the paper by Bernd-Olaf Küppers reprinted here, the reductionistic research program “is based on the central working hypothesis that all biological phenomena can be explained totally within the framework of physics and chemistry.” It assumes that there is no essential difference between non-living and living matter; life arises as a “quasi-continuous” transition requiring no additional epistemic principles other than those of physics and chemistry. Restrictions in our current understanding are merely the result of the complexity of the problem and its computability. Epistemic reductionism leads to ontological reductionism in which “life is nothing but a complex interplay of a large number of atoms and molecules.” Even consciousness must ultimately be reducible to physical laws.

To counter this program, some biologists and philosophers of science appeal to “emergence” and “downward causation,” claiming that genuinely novel properties and processes arise in highly complex phenomena. According to this view, physics is a necessary part of the explanation but it cannot provide a sufficient explanation on its own. Küppers summarizes the claims of emergence and downward causation, respectively, as follows: “(1) The whole is more than the sum of its parts. (2) The whole determines the behavior of its parts.”

Since these concepts seem “vague and mysterious” to scientists in physics and biology, Küppers focuses here on a general problem concerning the transition from the non-living to the living: can we adequately characterize the emergence of life in terms of the concept of complexity. Küppers thinks not, since non-living systems may themselves be extraordinarily complex. In addition, one may find evidence of emergence even within a field, such as within physics, and not just between fields.

In a similar way, those supporting intratheoretical reduction (e.g., reductionism within physics) frequently appeal to “bridge laws,” while defenders of emergence deny their availability and their fruitfulness. Arguments such as these also apply to the question of downward causation. In Küppers’ opinion, both emergence and downward causation are to be found within physics. Since no “non- physical principle” is involved, apparently, in the transition to life, Küppers concludes that “both (emergence and downward causation) must be thought of as characteristics of self-organizing matter that appear at all levels when matter unfolds its complexity by organizing itself.” Still, there are examples of biological systems, such as the DNA macromolecule, which are immensely more complex than complex physical systems. Do they point to a limitation in physical method or in the reductionistic research program, or will physics undergo a paradigm shift as it seeks to encompass these phenomena within its domain?

To understand these questions better, Küppers begins by distinguishing between laws and initial or boundary conditions in physical theory. His central claim is that “the complexity of a system or a phenomenon lies in the complexity . . . of its boundary conditions.” Following the analysis of Michael Polanyi, Küppers argues that in a human construction, such as a complex machine, the design, or boundary conditions, governs the physical processes but cannot be deduced from them. In this way a machine, by its structure and operation, is an emergent system, a whole which is “neither additive nor subtractive,” whose properties cannot be reduced to those of its components, and whose boundary conditions represent a form of downward causation. A similar case can be made for a living organism.

Now the question becomes, what determines the boundary conditions? For a machine, the answer is a blueprint. For the living organism, however, the “blueprint” lies in the organism’s genome which, in contrast to the machine, is an inherent part of the living system. Küppers then distinguishes complex from simple systems in terms of both their sensitivity to small changes in their boundary conditions and the uniqueness of these conditions, given all possible physically equivalent conditions.

The concept of boundary conditions thus becomes the key to understanding the paradigm shift that is occurring within physics regarding the problem of complex phenomena. This shift is not of the Kuhnian type, with its revolutionary change in the fundamental laws and the theoretical framework of a field. Instead it is an “internal shift of emphasis” within the given explanatory structure of the paradigm. As Küppers sees it, the shift of emphasis within the reductionistic research program consists in the move to regard the boundary conditions of complex phenomena as that which needs explanation. He calls this shift of emphasis the “paradigm of self-organization.” It entails a sequence of explanations, in which boundary conditions at one level (such as the boundary conditions of the DNA molecule) are ex plained by those of another level (such as the random molecular structures), which themselves need explanation. In effect, the nested structures found in living matter are reflected by the nested structures of the paradigm of self-organization.

Finally, Küppers points out that biological self-organization is only possible in the context of non-equilibrium physics. Still, though the existence of specific boundary conditions can be understood within the framework of physics, their detailed physical structure cannot be deduced from physics. “The fine structure of biological boundary conditions reflects the historical uniqueness of the underlying evolutionary process” and these, by definition, transcend the powers of natural law to describe.

Email link | Printer-friendly | Feedback | Contributed by: CTNS/Vatican Observatory